1. Field of Invention
The present invention relates to a driving circuit to drive an electro-optical panel, such as a liquid crystal panel, a method of testing a driving circuit, an electro-optical apparatus, such as a liquid crystal apparatus including an electro-optical panel and a driving circuit, and an electronic device, such as a liquid crystal projector including an electro-optical apparatus.
2. Description of Related Art
The related art drives an electro-optical panel by using a driving circuit integrally-formed or afterward-mounted on a substrate of the electro-optical panel. One related art technique of testing such a driving circuit is to check whether an image is correctly displayed on an electro-optical panel after completion of producing the electro-optical panel. However, in this technique, when an electro-optical panel has some defect, the defect is not detected until all the production processes are completed, because testing is performed after completion of the production process. Thus, this test method is disadvantageous from the point of view of cost. To avoid the above problem, before final testing is performed on the completed electro-optical panel, testing is generally performed on an array substrate in the middle of production process or before the array substrate is assembled into the final form of the electro-optical panel.
For example, in the case of an electro-optical apparatus having a driving circuit in the form of an integrated circuit produced separately and mounted thereon afterward, a probing test is performed on all integrated circuits to detect a line defect or the like before integrated circuits are mounted.
In the case of electro-optical apparatus having a built-in driving circuit, the operation of the driving circuit produced in the form of an internal circuit is tested before performing the probing test.
The driving circuit to drive the electro-optical panel includes, a data line driving circuit to drive data lines of the electro-optical panel, and a scanning line driving circuit to drive scanning lines of the electro-optical panel. The data line driving circuit and the scanning line driving circuit each include a shift register that sequentially generates, from respective stages thereof, transfer pulses from which to generate a sampling circuit driving signal to control an operation of sequentially driving data lines or a scanning signal to control a sequential scanning operation. For the purpose of reducing power consumption, the built-in driving circuit of the electro-optical apparatus is driven by a low voltage. Thus, the shift registers described above are also driven by a small voltage. Therefore, the voltage level of transfer pulses change within a small range. In order to obtain a swing large enough to drive matrix elements of the electro-optical panel, the voltage level of transfer pulses output from each shift register is shifted by a level shifter disposed at an output end of the shift register.
To test such a built-in circuit or a part thereof including shift registers and level shifters, an end pulse, specifically, a transfer pulse output from the final stage of a shift register is detected. In response, a signal output from one output terminal, which is selected as a test terminal from a plurality of output terminals of the level shifter, is examined.